Changes In Proline Content Research Articles

Diurnal changes in proline content of desert plants.

The diurnal changes in proline and water contents of Zygophyllum quatarense and Francoeuria crispa were investigated under desert conditions. In both plants, the proline content was low before sunrise amounting to 10.42 μmoles/g fresh weight in Zygophyllum and 6.3 μmoles/g fresh weight in Francoeuria. By the progress of the day and the intensification of the evaporative power of the atmosphere, the proline content increased considerably in the two plants. The proline content reached maximal values at 5 p.m., reaching 23.36 μmoles/g in Zygophyllum and 11.16 μmoles/g in Francoeuria. The proline content of the artificially watered plants was kept at a low level throughout the day. The conditions and role of proline accumulation were discussed.

The After‐Effect of Water Stress on Chlorophyll Formation during Greening and the Levels of Abscisic Acid and Proline in Dark Grown Wheat Seedlings

AbstractCut seedlings of wheat plants (Triticum aestivum L. cv. Starke II Weibull) between 6 and 7 days old were water stressed in darkness by exposing them to air of 35% relative humidity 2.5 to 20 h. This treatment resulted in a water potential of ‐11 bars in the leaves after 20 h. The leaves were then rewatered and irradiated. The chlorophyll formation that took place in fully turgid leaves during the greening was markedly decreased in the case of the water‐stress pretreatmet. and especially the lag phase was prolonged. The longer the stress pretreatment the more evident was the subsequent effect on chlorophyll formation. However, no linear relationship was found between the amount of stress and the chlorophyll content. Protochlorophyllide regeneration from endogenously formed δ‐aminolevulinic acid was markedly decreased even after the shortest water‐stress period. However, protochlorophyllide accumulation from exogenously supplied δ‐aminolevulinic acid was only slightly decreased following the water‐stress pretreatment. Further more, the ratio of protochlorophyllide650 to protochlorophyllide628 was slightly reduced by the same conditions.During the stress period both abscisic acid and proline were accumulated in the leaves. The content of abscisic acid increased up to six times the normal level during water stress lasting for 20 h. The increase of proline was about three‐fold for similar treatment. After rewatering the leaves the levels of both abscisic acid and proline rapidly declined and reached. 10 h later, the levels found in unstressed seedlings.The increase in abscisic acid during water stress associated with impaired chlorophyll metabolism suggested that the after‐effect of water stress might be linked to chlorophyll metabolism through abscisic acid or some of its metabolites. The changes in proline content open the possibility that this substance could function as a reserve substance for the formation of chlorophyll after the discon tinuation of the stress.

Proline Content and Metabolism during Rehydration of Wilted Excised Leaves in the Dark

Excised bean (Phaseolus vulgaris) leaves were used to measure changes in proline content and proline metabolism during rehydration in the dark after the leaves had been incubated in the dark 24 hours in a wilted condition.The increase in nonprotein proline which occurs in wilted leaves stopped immediately upon rehydration, and thereafter levels of proline declined. The rate of decline and the fate of the metabolized proline depended on the amount of carbohydrate present. When the level of carbohydrate was relatively high, the rate of decline in proline content was slow, and the proline was converted mainly to protein proline. When the level of carbohydrate was relatively low, the rate of proline decline was rapid and a large percentage of the proline was oxidized to CO(2) and other amino acids in addition to conversion to protein proline.The results indicate that nonprotein proline can be oxidized when the level is increased by endogenous synthesis. Proline oxidation has been observed when the levels are increased by adding exogenous proline. Oxidation of endogenous proline is inhibited by carbohydrates in the leaf, as is true of oxidation of exogenous proline.